Impact hammer for liner printer

ABSTRACT

A plastic injection molded hammer for line printers is disclosed. The hammer comprises a tapered body and a hammer head projecting at approximately a right angle from the logitudinal dimension of the hammer body. The hammer body is hollow with an opening in the back of the body. The coil and core of an electromagnet are seated in the hollow portion of the body through the opening in the back of the body and an armature is embedded in the base of the body directly below the coil and core. In operation, the armature is attracted to the coil and the core, when the coil is energized, with such great force that the face of the hammer is whipped against the print anvil.

United States Patent 1191 Perry 14 1 Feb. 6, 1973 IMPACT HAMMER FOR LINER 3,418,928 12/1968 Ponzano ..101/93 0 PRINTER 3,434,413 3/1969 Lee et al. lOl/93 C 1 1 inventor: Richard Anthony My, Anebom, 21232133? 211333 EEEZLZZIIIJJI..................:::::181/32E Mass. [73] Assignee: Odec Computer Systems, Inc., East Primary Examine''*wmiam p id R Attorney-William Frederick Werner [21] Appl' 82355 A plastic injection molded hammer for line printers is disclosed. The hammer comprises a tapered body and [52] U.S.Cl. ..l0l/93C a hammer head P j g at approximately a right [51] Int. Cl. ..B4lj 9/38 angle from the iogitudinal dimension of h h mm r [58] Field of Search ..l01/93 C, 10; 335/220 y- The h mmer body is hollow with an Opening in the back of the body. The coil and core of an elec- [56] References Cited tromagnet are seated in the hollow portion of the body through the opening in the back of the body and an UNITED STATES PATENTS armature is embedded in the base of the body directly 3,001,469 9/l96i Davis et al. ..101 93 c below the and core- 1 armature is 3 149 562 9 19 4 Wilkins 1 un 93 attracted to the coil and the core, when the coil is 3,228,325 1/1966 Miller ..10l/93 C energized, with such great force that the face of the ,23 .54 966 Groltrup... .....l0l/93 C hammer is whipped against the print anvil. 3,30l,l77 l/l967 Shepard.... .....lOl/93 C 3,349,696 10/1967 Potter ..i()l/93 C 3 Claims, 11 Drawing Figures PAIENTEDFEB 6 ma 3, 714,892

INVENTOR RICHARD ANTHONY PERRY ATTORNEY print hammer for line BACKGROUND OF THE INVENTION This invention relates to impact hammers and more particularly to a plastic impact hammer and electromagnet combination for use with line printers.

In high speed printers it is necessary that the forward and backward motion of the print hammer be very rapid in order to obtain a high printing speed and neat and perfectly aligned print. Furthermore, the hammer must obviously be so constructed that its path of travel is always the same. That is, the hammer cannot be permitted to bend sideways; the distance that it travels must always be the same; and the hammer must be so constructed that the hammer face properly strikes the anvil on every stroke.

Various different hammer arrangements are available on the market today. Generally these prior art hammers are constructed of metal and the hammers are actuated by an electromagnet arrangement. Return springs are used to return the hammer to its rest position. In some other arrangements the hammer is spring loaded and held off by the electromagnet. In this type of hammer structure the hammer is driven by the energy in the spring when the power is removed from the electromagnet. A third type of prior art hammer mechanism operates by whipping the hammer against the anvil. Such hammers are described in U.S. Pat. No. 3,301,177 to Shepard, Jr., and in US. Pat. No. 3,513,773 to Ponzano. The invention described herein is related to this third type of hammer arrangement and is an improvement over such prior art hammers.

SUMMARY OF THE INVENTION This invention comprises a plastic injection molded hammer and electromagnet arrangement. For strength and resiliency a nylon plastic may be utilized to fabricate the hammer.

The hammer body is so constructed that it is hollow with an opening in the back part of the hammer body. The'coil and core of the electromagnet are positioned in the hammer body through the opening in the back of the body. The hammer head is integrally formed with the body and projects at approximately a right angle from the longitudinal dimension of the body. An armature is molded and embedded in the base of the hammer body in such a manner that the armature is positioned directly below the coil and core of the electromagnet. The hammer and electromagnet arrangement of this invention is easily manufactured and is relatively low in cost.

When the coil is energized, the armature is attracted to the coil and core with a great force. When the armature is attracted to the coil and the core, the hammer face moves from a rest gap position with respect to the print anvil to a stop gap position. However, the momentum is so great that the hammer body bends and whips or throws the hammer face into contact with the print anvr It is therefore an object of this invention to provide a hammer for a line printer.

It is another object of this invention to provide a printers that is easily manufactured and relatively low in cost.

A further object of this invention is to provide a whip action hammer for a line printer.

A still further object of this invention is to provide a plastic injection molded print hammer for line printers. A further object of this invention is to provide a hammer and electromagnet combination for line printers. a

BRIEF DESCRIPTION OF THE DRAWING- Y view of the hammer and electromagnet of FIG. 1;

FIG. 4 shows the hammer and electromagnet with the coil and core of the electromagnet removed from a the hammer body;

FIG. 5 is a cross sectional view of the hammer and the coil of the electromagnet; FIG. 6 is a cross sectional view showing how the armature of the electromagnet is embedded and molded into the hammer body;

FIG. 7 is a fractional cross sectional view showing in detail a portion of the hammer body;

FIG. 8 is a side view showing the hammer in its rest position with respect to the print anvil;

FIG. 9 is a side view showing the hammer in its intermediate position withrespect to the print anvil;

FIG. 10 is a side view illustrating the hammer bending to strike the print anvil; and

FIG. 11 is a fractional view of the hammer ing the taper of the hammer face..

DESCRIPTION OF THE INVENTION Broadly, the hammer of this invention comprisesa hammer 1 having a body 2, a hammer head 4 and a hammer face 6. The electromagnet arrangement com prises a coil 8 and a core 10 partially housed within body 2 of the hammer and an armature l2 embedded in a the base of the body. Before going into a detailed description of the structural features of the hammerand the electromagnet combination, the manner in which the hammer operates will first be described because the significance of some of thestructural features of the hammer become more apparent when the operation is fully understood. 'The operation will be described with reference to FIGS. 8, 9 and 10.

FIGS. 8, 9 and 10 all show a side view of the hammer and the electromagnet combination and in addition show a print anvil 5. FIG. 8 shows the hammer in its rest position; FIG. 9 shows the hammer in an .intermediate position and FIG. 10 shows the hammer striking print anvil 5. As shown in FIG. 8 hammer l is in its rest position and coil 8 is deenergi zed. In this position hammer face 6 is removed from anvil 5 by the rest gap A distance indicated by the arrows 77. When the coil is energized, armature 12 is attracted to coil 8 and core 10 and hammer face 6 moves from its rest gap A position to a stop gap position B indicated by the arrows 7'7 in FIG. 9. However, due to the fact that armaillustrat- I ture 12 is attracted to coil 8 and core 10 with a very great force, hammer body 2 bends and whips face 6 of hammer head 4 against print anvil 5 as shown in FIG. 10. During this operation hammer 1 travels from zero or standstill to approximately 60 miles an hour. Therefore, it is quite apparent that the force of attraction on armature 12 is very great. After striking anvil 5, hammer l returns to its rest position due both to its resiliency and the restoring force of wire spring 22.

Now that the operation has been described the structural features of the hammer and electromagnet will be described in detail. Hammer 1 is fabricated preferably from a nylon plastic and is formed by injection molding. While other compositions may be used, a nylon plastic of 30 percent glass filled ZYTEL nylon has been found ideally suitable for fabricating a hammer having a high degree of strength and resiliency. Body 2 of hammer 1 tapers downward from the base of the body to hammer head 4. The taper in the body gives uniformity between degree of bend between hammers. A major portion of body 2 is hollow and open in the back as is clearly shown in FIGS. 3,4, and 5. To provide additional strength a shelf 26 is provided across the inside of body 2. Hammer head 4 projects approximately at a right angle from the narrow end of body 2 and terminates in a hammer face 6. Hammer face 6 is secured by means of a pin 28 that is integrally formed with face 6 and is embedded into hammer head 4 as shown in FIG. 5.

The overall electromagnet structure comprises coil 8, core 10 and armature l2. Armature 12 is molded and embedded into the base of body 2 as shown in FIG. 6. Core 10 is essentially an H-shaped core and coil 8 is wrapped around one of the legs of the core. Leads 18 are provided to energize coil 8. A spring 20 is slipped over the other leg of core 10. Spring 20 is so shaped that it wraps around the leg of core 10 and has arms 22 that project below core 10. Arms 22 of spring 20 wrap around and rest on the bearing surfaces 30 that are integrally formed on core 10. The coil, core and spring assembly is slipped into the opening in the back of hammer body 2 and is secured to the body by means of pin 32. Bearings 30 pressed into core 10 provide bearing support for pin 32, A cut out A is provided, as needed, to add resiliency in body 2. The manner in which the coil, core and spring arrangement is secured in hammer body 2, is not critical since as is obvious from the above description of the operation, the pin or other securing means do not move. Therefore any suitable securing means can be utilized to secure the .coil, core and spring assembly in hammer body 2.

When the coil, core and spring assembly is secured in body 2 the arms 22 of spring 20 rest on the ledges 24 formed inside of hammer body 2. This is clearly shown in FIG. 10. These ledges are provided to prevent the spring from scraping against the top surface of the armature. if the spring scraped the surface of the armature, it is apparent that the spring would wear the annature into fine iron filings which could interfere with the magnetic field and therefore the electromagnet operation. In addition, although not shown in the drawing, the top surface of armature 12 may be coated with a thin layer of Mylar to provide a high reluctance path to prevent the holding of armature 12 by the coil and core assembly due to residual magnetism that may be this invention provides a one part hammer that requiresnone of the prior art stop devices to stop the hammer in its movement toward the printing surface. it is easily manufactured and is relatively inexpensiveto manufacture. When hammer face 6 is whipped 'or thrown against anvil 5 as shown in FIG, 10 it returns to its rest position due to the resiliency of hammer body 2-. Spring 20 is not used to pull the hammer away from anvil 5.

This spring is used to pull coil 8 and core 10 away from armatures 12 to rest position in relation to the coil 8 after the hammer head face 6 has struck the anvil 5; ZYTEL nylon is a theme-plastic.

While the invention has been describedwith reference to a specific embodiment, it will be apparent to those skilled in the art-that various changes-and modifications can be made to the preferred embodi-- ment without departing from the spirit and scope of the invention as definedin the following claims:

What is claimed is: 1. A plastic hammer and electromagnet combination comprising, a molded plastic hammer having a tapered hollow body open in the back and a hammer head pro- I jecting from one end of said body; and an electromagnet having an armature embedded in the base of said body and a coil and core combination partially secured inside said hollow body directly above said armature, a

pivot member'on said core portion received within said hollow body, said hammer having bearing ineans pivotally mounted on said pivot member, ledges formed inside said hollow body along said armature, a

spring having two arms, and means attaching said spring to said core with said two arms slidably resting on said ledges.

2. A plastic hammer for a line printer comprising, a hollow body open in the back and having a base on one end and a neck portion near the other end, said body tapering downward from said base to said neck portion,

a hammer head integrally formed with said neck portion and projecting outward from said body, a hammer face secured to said hammer head, a shelf formed inside said body in said neck portion and a pair of ledges formedinside said hollow body near said basefan armature embedded in said base, a coil and core combination partially secured inside said hollow body above said armature, a pivot member fastened to said core and received within said hollow body, said hammer having bearing means pivotally mounted on said pivot member, a spring having two arms, and means attaching said spring to said core with said two arms slidably resting on said ledges.

3. A hammer as described in claim 2, wherein said hammer is fabricated from a plastic containing approximately thirty percent by volume of glass fibers.

8 t i 8 i 

1. A plastic hammer and electromagnet combination comprising, a molded plastic hammer having a tapered hollow body open in the back and a hammer head projecting from one end of said body; and an electromagnet having an armature embedded in the base of said body and a coil and core combination partially secured inside said hollow body directly above said armature, a pivot member on said core portion received within said hollow body, said hammer having bearing means pivotally mounted on said pivot member, ledges formed inside said hollow body along said armature, a spring having two arms, and means attaching said spring to said core with said two arms slidably resting on said ledges.
 1. A plastic hammer and electromagnet combination comprising, a molded plastic hammer having a tapered hollow body open in the back and a hammer head projecting from one end of said body; and an electromagnet having an armature embedded in the base of said body and a coil and core combination partially secured inside said hollow body directly above said armature, a pivot member on said core portion received within said hollow body, said hammer having bearing means pivotally mounted on said pivot member, ledges formed inside said hollow body along said armature, a spring having two arms, and means attaching said spring to said core with said two arms slidably resting on said ledges.
 2. A plastic hammer for a line printer comprising, a hollow body open in the back and having a base on one end and a neck portion near the other end, said body tapering downward from said base to said neck portion, a hammer head integrally formed with said neck portion and projecting outward from said body, a hammer face secured to said hammer head, a shelf formed inside said body in said neck portion and a pair of ledges formed inside said hollow body near said base, an armature embedded in said base, a coil and core combination partially secured inside said hollow body above said armature, a pivot member fastened to said core and received within said hollow body, said hammer having bearing means pivotally mounted on said pivot member, a spring having two arms, and means attaching said spring to said core with said two arms slidably resting on said ledges. 